1. Field of the Invention
The present invention relates to an extensible host controller and an operation method thereof, and particularly to an extensible host controller and an operation method thereof that can make a universal serial bus (USB) host communicate with another USB host through an ordinary USB transmission line.
2. Description of the Prior Art
The universal serial bus (USB) technique is an industry standard developed in mid-1990s that defines an external expansion bus which makes computer peripherals facilitate to connect to a host (e.g. a personal computer). Because the USB technique utilizes a master/slave architecture, a USB host controller of the host acts as a master role to send requests to a USB peripheral device (that is, a computer peripheral), and the USB peripheral device acts as a slave role to respond the requests from the host. The above mentioned master/slave roles are asymmetric and irreversible in a standard USB environment.
It is impossible to directly communicate between two hosts under the master/slave architecture except using an intermediate bridge device with both side slave interfaces. However, the intermediate bridge device is more expensive than an ordinary USB transmission line, and data transmission performance between the two hosts is limited due to indirect data transmission of the intermediate bridge device. Therefore, the intermediate bridge device is not proper to act as a communication Role between the two hosts.